The railroad industry, because of its time extensive nature, is inherently resistant to quick fixes presented by untested technological changes. Railroad tracks and rolling equipment are effected by a variety of subtle factors made important by the repetitive nature of the industry.
Those of normal skill in the railroad industry are those who are particularly qualified in the art of discernment and recognize that subtle and hard to identify factors are more important to this industry than they may be in other industries. Those of less than ordinary skill in the field of concern may fail to recognize the subtle factors of importance and assume that some particular improvement may make another improvement obvious when, in fact, those of ordinary skill would recognize such change as highly innovative.
One of the more perplexing problems that the railroad industry has learned to live with relates to interfacing a track system needing dimensional stability with a supporting surface which is dimensionally unstable. The developed technology generally calls for bedding material, called ballast, to be placed on a prepared earthen surface; ties to be placed on the bedding material; and rails atttached to the ties. Ideally the system is structured so that relative motion between the surface, the bedding material and the ties is absorbed in a manner that leaves the rails parallel and neither warped nor humped. Some of the relative motion results from weather factors effecting the supportive surface and other relative motion results from imposed work loads. The imposed stresses are of repetitive nature and, like water wearing away stone, the system erodes with time.
The weather factors that influence supporting surface movement include a 22 year drought and flood cycle, seasonal changes with an annual cycle and, within each seasonal cycle, a day/night change. Local weather can, in a few minutes and in a distance of a few hundred yards, combine the extremes of the 22 year cycle, the annual cycle and the daily cycle into one brief occurance.
Severe thunderstorms have been known, for example, to bury one section of track under icy hail with the surface awash due to run-off rain; and leave the adjoining section of track resting on a dry, hard packed surface with the rails exposed to the scorching heat of the sun. Thus the weather variables may be experienced over a period of almost a quarter century or within minutes.
Technological changes relative to railroad rolling stock as well as track systems also produce many variable and subtle effects. Track wear patterns have changed as different alloys of metal have been introduced. Other subtle changes have resulted in the change from steam driven locomotives to diesel engines; as passenger trains have been phased out in favor of freight trains; as operational speeds have been varied; and as changes in decelerative techniques have been made. Expansive details on the Background of the Invention can be found in U.S. patents in Class 238 and related classes. Pursuit of such details reveal that many piecemeal solutions have been tried and found wanting but a long felt need exists for synergistic solutions. In particular there is a long felt need to accomodate longitudinal changes in rail length, brought about by temperature changes, without introducing stresses that result in lateral warping or vertical humping which introduce failure factors to the underlying supportive surface.
To be truly synergistic the accomodations for the result of temperature changes should also be responsive to wear factors felt by rolling stock, tracks, ties and bedding material. Those of normal skill in the field of concern will appreciate the fact that subtle nuances within the technology do much to seperate the obvious improvements from those which are not.